Flashback arrestor

ABSTRACT

A flashback arrestor for use in gas cutting or welding equipment includes a porous body which defines a proximal end portion and a distal end portion and which has a plurality of pores. Each of the pores defines a pore size. The pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the sintered body.

FIELD

The present disclosure relates to oxy-fuel cutting or welding equipmentand more specifically to flashback arrestors for the oxy-fuel cutting orwelding equipment.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Oxy-fuel cutting or welding torches generally employ oxygen and a fuelgas, such as acetylene or propane, by way of example, to cut or weld aworkpiece. The oxy-fuel torch is generally connected to an oxygen hosethat supplies preheat and cutting oxygen, and a fuel gas hose thatsupplies fuel, to the cutting or welding torch. Preheat oxygen and thefuel gas are mixed in the cutting or welding torch and ignited toprovide heat to the workpiece. Cutting oxygen may be added to react withthe heated workpiece to initiate a cutting process.

While the oxy-fuel cutting or welding torches have proven to berelatively safe if operated properly, an inherent hazard, known as“flashback”, is present in the process. Flashback can occur when oxygenenters the fuel side of the system or vice versa due to a reverse flow.The mixed gases, if ignited, can cause a flame to retreat into the torchhandle or even the gas hoses and can cause an explosion at any point inthe system.

One solution to this problem is to install a check valve in each of theoxygen and fuel passageways to allow the oxygen and the fuel to flow inone direction to prevent the reverse flow. Check valves, however, aremechanical devices and may become unreliable when contaminated with dirtor debris, which can cause the check valve to leak. Moreover, the checkvalves cannot prevent flashback flame from propagating upstream onceflashback occurs.

Another solution to this problem is to use a flashback arrestor (FBA).FBAs do not prevent flashback from occurring, but can stop the flashbackflame from further propagating beyond the FBA and into the oxygen/fuelhoses or other components in the oxy-fuel cutting or welding system. TheFBA generally includes a stainless steel filter that removes heat andfree radicals from a flame at a rate that is fast enough to quench theflame and to prevent re-ignition of the hot gas.

The FBAs, however, have the disadvantage of being easily clogged withdebris. The stainless steel filter used in a typical FBA is a porousbody generally having a pore size of approximately 7 μm (0.000276 inchesin diameter), which is about 1/14 the size of a human hair (0.004 inchesin diameter). Due to such fine pore size of the filter, FBAs can beeasily clogged with debris. Moreover, the FBAs are installed in theoxygen and fuel gas passageways in the torch and can restrict flow ofthe oxygen and fuel gases due to the fine pore size. Therefore, thetorch performance is adversely affected.

SUMMARY

In one form of the present disclosure, a flashback arrestor for use ingas cutting or welding equipment includes a porous body defining aproximal end portion and a distal end portion and having a plurality ofpores. Each of the pores defines a pore size. The pore size is afunction of a detonation cell size such that the pore size is increasedto reduce a size of the sintered body.

In another form of the present disclosure, a flashback arrestor for usein gas cutting or welding equipment includes a body defining a proximalend portion and a distal end portion and having a plurality of pores.Each of the pores defines a pore size. The pore size is a function of adetonation cell size such that the pore size is increased to reduce asize of the body.

In still another form of the present disclosure, a device for arrestinga flame includes a body having a plurality of pores. Each of the poresdefines a pore size. The pore size is a function of a detonation cellsize such that the pore size is increased to reduce a size of the body.

In still another form of the present disclosure, a flashback arrestorfor use in gas cutting or welding equipment includes a sintered body anda fitting. The sintered body defines a proximal end portion and a distalend portion and having a plurality of pores. Each of the pores defines apore size. The fitting is disposed at the proximal end portion. Thefitting is sized to fit within a bore of a standard pipe thread. Thepore size is a function of a detonation cell size such that the poresize is increased to reduce a size of the sintered body.

In still another form of the present disclosure, an oxy-fuelcutting/welding torch includes a torch body defining a proximal endportion and a distal end portion, an oxygen passageway having an inletat the proximal end portion, a fuel passageway having an inlet at theproximal end portion, a first flashback arrestor disposed within theoxygen passageway at the proximal end portion, and a second flashbackarrestor disposed within the fuel passageway at the proximal endportion. Each of the first and second flashback arrestors defines a bodyhaving a proximal end portion and a distal end portion and includes aplurality of pores. Each of the pores defines a pore size. The pore sizeis a function of a detonation cell size such that the pore size isincreased to reduce a size of the body.

In another form, a device for arresting a flame is provided thatcomprises a body having a plurality of pores, each of the pores defininga target pore size, wherein the pore size is a function of an initialpressure of a gas mixture and an equivalence ratio of the gas mixturesuch that the pore size is increased to reduce a size of the body.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a cross-sectional view of a prior art flashback arrestormounted internally within a torch body;

FIG. 2 is an exploded view of a prior art flashback arrestor;

FIG. 3 is a cross-sectional view of another prior art flashback arrestorcontained in a safety device external to a cutting torch;

FIG. 4 is a top view of an oxy-fuel cutting/welding torch includingflashback arresters constructed in accordance with the teachings of thepresent disclosure;

FIG. 5 is a cross-sectional view of the oxy-fuel cutting/welding torch,taken along line 5-5 of FIG. 4;

FIG. 6 is a cross-sectional view of a flashback arrestor mountedinternally within a torch body and constructed in accordance with theteachings of the present disclosure;

FIG. 7 is an exploded view of the flashback arrestor of FIG. 6;

FIG. 8 is a cross-sectional view of another form of a flashback arrestorcontained in a safety device external to a cutting torch and constructedin accordance with the teachings of the present disclosure;

FIGS. 9A and 9B are perspective views of another form of the flashbackarrestors having end caps and constructed in accordance with theteachings of the present disclosure;

FIG. 10 is a schematic view of detonation cells and shock wave duringdetonation;

FIG. 11 are graphs of relationships among oxy-acetylene cell width,critical tube diameter and initial pressure;

FIG. 12 is a graph of the relationship between the detonation cell widthand the initial pressure when the oxy-acetylene (C₂H₂-O₂) mixture isunder stoichiometric condition;

FIG. 13 is a graph of the relationship between the detonation cell widthand the initial pressure when the equivalence ratio of the C₂H₂—O₂mixture is 2.5;

FIG. 14 is a graph of the relationship between the detonation cell widthand the equivalence ratio of the C₂H₂—O₂ mixture;

FIG. 15 is a graph of the relationship between the detonation velocityand the fuel volume % of the C₂H₂—O₂ mixture; and

FIG. 16 is graph of the relationship between the detonation velocity andthe tube diameter for different oxy-acetylene mixtures.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features. Itshould also be understood that various cross-hatching patterns used inthe drawings are not intended to limit the specific materials that maybe employed with the present disclosure. The cross-hatching patterns aremerely exemplary of preferable materials or are used to distinguishbetween adjacent or mating components illustrated within the drawingsfor purposes of clarity.

Referring to FIGS. 1 and 2, a pair of typical flashback arrestors 10 areinstalled in a torch body 12 of a cutting or welding torch (not shown).The torch body 12 defines an oxygen passageway 14 and a fuel gaspassageway 16. The pair of flashback arrestors 10 each includes a porousmetal portion 18, a fitting 20, and a check valve 22. The fitting 20includes a bore 24 in fluid communication with the oxygen passageway 14or the fuel gas passageway 16. The fitting 20 includes a proximalthreaded portion 26 and a distal threaded portion 28. The check valve 22is disposed in the bore 24 proximate the proximal threaded portion 26.The proximal threaded portion 26 has an outside diameter D1 andfunctions as a hose connector for connecting to an oxygen or fuel gashose (not shown). The distal threaded portion 28 engages an innersurface of the torch body 12 to secure the flashback arrestor 10 to thetorch body 12 via a threaded connection. The distal threaded portion 28has an outside diameter D2 which is greater than the outside diameter D1of the proximal threaded portion 26. An insertion portion 29 is providedproximate the distal threaded portion 28 and inserted into the porousbody 18.

An O-ring 31 is disposed in an annular groove 32 (shown in FIG. 2) ofthe fitting 20. When the fitting 20 is installed in the torch body 12,the O-ring 31 prevents leakage of gas from the oxygen passageway 14 andthe fuel gas passageway 16 to outside the flashback arrestors 10. Amounting assembly 36, which includes a mounting plate 38, a washer 40,and a screw 42, is used to secure the flashback arrestors 10 to thetorch body 12.

Referring to FIG. 3, another form of typical flashback arrestors 50 aremounted to a pair of add-on devices, i.e., safety devices 52 separatefrom the cutting/welding torch. The safety devices 52 each include ahousing 54 and a bore 56. The flashback arrestor 50 is inserted into thebore 56 of the housing 54 and includes a porous body 58, a bushing 60,and a check valve 62. The housing 54 includes a proximal threadedportion 64, which functions as a hose connector for engaging an oxygenor fuel gas hose. The bushing 60 includes a distal threaded portion 66for engaging an inner surface of the housing 54 of the safety device 52.An O-ring 68 is provided between the housing 54 and the bushing 60 toprevent leakage of gas to outside the flashback arrestor 50. An adaptor72, in the form of a hose nipple, has one end inserted into a hosefitting nut 70 and the other end inserted into the bushing 60 to mountthe safety device 52 to the hose fitting nut 70. The distal threadedportion 66 of the bushing 60 has an outside diameter D4 greater than theoutside diameter D3 of the proximal threaded portion 64 of the add-ondevice 52.

In the typical flashback arrestors 10 and 50, the porous bodies 18 and58 have a pore size of approximately 7 μm. This pore size is based onthe indicated pores size from ISO 4003 bubble point testing. Bubblepoint testing indicates the pore size is based on “capillary theory” andcylindrical capillary tube data. The indicated pore size is related tothe bubble point pressure based on Poiseuille's law which incorporatesan empirical constant that is a function of the filter material, form,etc. This constant is essentially a capillary shape factor. Therefore,the bubble point testing is typically only a relative comparison for agiven element or medium. In various forms, the true pore size is likely2 to 5 times smaller than that indicated by bubble point test results.

Referring to FIGS. 4 and 5, an oxy-fuel cutting/welding torch thatincludes flashback arrestors constructed in accordance with theteachings of the present disclosure is generally indicated by referencenumeral 100. The cutting or welding torch 100 includes a torch head 102and a handle portion 104. The handle portion 104 includes a torch body106 and a barrel 108. The oxy-fuel cutting/welding torch 100 furtherincludes a preheat fuel tube 112, a preheat oxygen tube 114, and acutting oxygen tube 116 extending from the torch head 102 to the barrel108 for supplying fuel gas and preheat/cutting oxygen to the torch head102. A lever 118 is connected to the torch body 106 for controlling agas valve 146. A pair of flashback arrestors 130 (only one is shown inFIG. 4) are removably mounted to the torch body 106.

Referring to FIG. 5, the torch head 102 includes a cutting/welding tip132. The torch body 106 defines a fuel gas bore 134, an oxygen bore 136,a fuel gas passageway 138, and an oxygen passageway 140. The fuel gaspassageway 138 is provided between the fuel gas bore 134 in the torchbody 106 and the fuel gas tube 112 in the barrel 108 to provide fluidcommunication therebetween. The oxygen passageway 140 is disposedbetween the oxygen bore 136 in the torch body 106 and the preheat oxygentube 114 (shown in FIG. 4) in the barrel 108 to provide fluidcommunication therebetween. The oxygen passageway 140 also providesfluid communication between the oxygen bore 136 and the cutting oxygentube 116. A fuel gas hose 142 (which has left-hand threads) and anoxygen hose 144 are connected to the flashback arresters 130 to supplyfuel gas and oxygen, respectively, to the fuel gas bore 134 and theoxygen bore 136. Fuel and oxygen valves 146 are provided at the torchbody 106 to control flow of fuel or oxygen from the fuel gas bore 134 orthe oxygen bore 136 to the fuel gas and oxygen passageways 138 and 140.

Referring to FIG. 6, the flashback arrestors 130 constructed inaccordance with the teachings of the present disclosure each include aporous body 150, a fitting 152, and a check valve 154. The flashbackarrestors 130 are inserted into the fuel gas bore 134 and the oxygenbore 136 in the torch body 106 for arresting and quenching flames when aflashback occurs.

The fittings 152 each include a proximal threaded portion 156, a distalthreaded portion 158 and an enlarged portion 160 therebetween. Theproximal threaded portion 156 has outer threads for engaging the fuelhose 142 or the oxygen hose 144 (shown in FIG. 5). The distal threadedportion 158 has outer threads for engaging inner threads of the torchbody 106 such that the flashback arrestors 130 are secured to the torchbody 106 via threaded connection. The proximal threaded portion 156 hasan outside diameter D5 and in one form is sized to fit within a bore ofa standard pipe thread, which is a ¼-18 National Pipe Thread (NPT).

The check valve 154 is press-fitted inside the bore 168 of the fitting152 proximate the proximal threaded portion 156 and allows oxygen orfuel gas to flow in one direction, i.e., from the oxygen/fuel gas hoses,through the fittings 152 to the porous bodies 150.

The porous body 150 of the flashback arrestor 130 is, in one form, acylindrical body and is formed by a sintering process. In one form, thematerial for the porous body 150 is a stainless steel grade 316.However, it should be understood that a variety of materials having ahigh thermal conductivity may be employed, including other metallicmaterials such as nickel, brass, bronze, and alloys thereof, amongothers.

The porous body 150 defines a proximal end portion 162 and a distal endportion 164 and a bore 166 extending therebetween. The bore 166 of theporous body 150 is in fluid communication with the bore 168 of thefitting 152. The porous body 150, in one form, is press-fit into thedistal threaded portion 158 of the fitting 152.

As further shown, the proximal end portion 162 of the porous body 150has an open end, whereas the distal end portion 164 of the porous body150 has a closed end with a distal face 168. The porous body 150 definesa plurality of pores. The bore 166 of the porous body 150 is in fluidcommunication with the fuel gas passageway 138 (shown in FIG. 5) or theoxygen passageway 140 (shown in FIG. 5) through the pores of the porousbody 150. The pores have irregular shapes and define passageways throughthe porous body 150. The pores define a pore size, which is a functionof a detonation cell size λ such that the pore size is increased toreduce a size of the sintered porous body. As an example, the pore sizeis between approximately 10 μm and approximately 16 μm. Because the poresize of the present disclosure is greater than the pore size (7 μm) in atypical flashback arrestor, the outside diameter of the porous body 150can be made smaller than that of the porous body in a typical flashbackarrester for a predetermined flow capacity. As such, the distal threadedportion 158 of the fitting 130 proximate the porous body 150 can also bemade smaller than that of a fitting in a typical flashback arrestor. Inthe embodiment of FIG. 6, the distal threaded portion 158 has an outsidediameter equal to or smaller than the outside diameter D5 of theproximal threaded portion 156. The porous body 150 of the presentdisclosure has a reduced outside diameter and an increased pore size.

The flashback arrestor 130 may further include a check valve 170disposed within the fitting 152. The fitting 152 is used to secure thecheck valve 154 to the torch body 106. Therefore, no O-ring oradditional mounting assembly is needed to mount the flashback arrestors130 to the torch body 106.

Referring to FIG. 7, the flashback arrestors 130 constructed inaccordance with the teachings of the present disclosure have fewercomponents than the typical flashback arrestors 10 of FIG. 2. As shownin FIG. 2, the typical flashback arrestors 10 require a pair of O-rings31 and a mounting assembly 36, which includes a mounting plate 38, awasher 40 and a screw 42, to mount the flashback arrestors to the torchbody 12. In contrast, as shown in FIG. 7, the flashback arrestors 130 ofthe present disclosure can be mounted to the torch body 12 without usingO-rings and the mounting assembly.

Referring to FIG. 8, another form of a flashback arrester 200 isprovided in an add-on device, i.e., a safety device 202 external to thehose fitting 206. The safety devices 202 are mounted to the hose fitting206 by adapters 215 in the form of a hose nipple. The flashbackarrestors 200 include a porous body 204, a fitting 207 and a check valve208. The safety device 202 has a proximal portion 210, a distal portion212 and a bore 205 therebetween. The adaptor 215 has one end insertedinto the hose fitting nut 206 of the oxy-fuel cutting/welding torch andanother end inserted into the bore 214 proximate the distal portion 212of the add-on device 202 to mount the safety device 202 to the hosefitting nut 206. The fitting 207 includes a proximal threaded portion214, a distal threaded portion 216, and an enlarged portion 218therebetween. The proximal threaded portion 214 has an outside diameterD6. The distal threaded portion 216 may have an outside diameter equalto or smaller than the outside diameter D6 of the proximal threadedportion 214. The distal threaded portion 216 engages an inner threadedportion 220 of the safety device 202 via threaded connection such thatthe flashback arresters 200 are secured to the safety device 202. Theflashback arrestors 200 are disposed outside the safety device 202except the distal threaded portion 216. The porous body 204 includes aproximal end portion 230 and a distal end portion 232. The proximal endportion 230 is inserted into the bore 236 of the fitting 207 proximatethe distal threaded portion 216. The distal end portion 232 is a closedend including a distal face 234. The check valve 208 is press-fittedinto the bore 236 of the fittings 207.

Referring now to FIGS. 9A and 9B, the flashback arrestors 130 in anotherform may also be provided with end caps 172, which are secured to adistal end portion of the porous bodies 150 as shown. In this form, theporous bodies 150 have open end portions rather than closed ends aspreviously set forth, which allows for improved manufacturability. Morespecifically, the porous bodies 150 can be formed in a continuous lengthand subsequently cut to size according to the specific torchapplication. The end caps 172 are a similar or the same material as theporous bodies, namely, a sintered metal material in one form. The endcaps 172 may be press fit into the porous bodies 150, or they may bebonded in another form of the present disclosure.

The pores of the porous body of the flashback arrestors 130 and 200constructed in accordance with the teachings of the present disclosurecan be used to arrest both deflagrations and detonations. The pore sizeof the pores is a function of a detonation cell size λ.

Flashback in an oxy-fuel system is the propagation of combustion thattravels in a reverse direction of the normal gas flow. The propagationof combustion undergoes two phases: a deflagration phase and adetonation phase. During the deflagration phase, the flame first entersthe torch and progressively increases in velocity. The velocity of theflame during the deflagration phase is at a rate below mach 1 (i.e.,subsonic velocity); however, the velocity of the flame continues toincrease until it reaches mach 1 (sonic velocity). Once the velocityreaches sonic speed, a deflagration-to-detonation transition (DDT) canoccur with associated abnormally high velocities and pressures.

The detonation phase ensues and continues to increase in velocity beyondmach 1 (supersonic velocity). The distance the flame travels during thephase change from deflagration to detonation is known as the inductionlength. Testing reveals that the induction length is very short andoccurs approximately 0.5″ to 0.7″ from the tip end of the torch.

When a detonation phase is reached, a large amount of energy is releasedand the propagation rate of the combustion process becomes supersonic.Testing reveals that the propagation rate of a detonation can reach3,000 meters/second.

Referring to FIG. 10, as the combustion propagates during the detonationphase, detonation cells are created and continue to generate andre-establish themselves. Detonation cells represent the 3-D structure ofthe detonation wave, which has a detonation cell size or width λ. Thedetonation cell size λ is a function of the composition of the mixture,initial temperature and pressure, and the types of the fuel (such aspropane, propylene, natural gas) and the oxidizer (such as oxygen). Forexample, the detonation cell size λ increases as the initial pressuredecreases. The pore size of the porous body also depends on the oxy-fuelmixture. When the mixture of fuel and oxygen is more susceptible todetonation, the detonation cell size is relatively smaller. Therefore,the pore size should be smaller for effective arrestment of detonationfor more volatile mixture.

The pore size of the porous body 150 in accordance with the teachings ofthe present disclosure is determined based on the detonation cell widthλ, which is a function of the composition of the mixture, initialtemperature and pressure, and the types of the fuel and the oxidizer.The pore size of the porous body 150 can effectively disruptregeneration of detonation cells to thereby extinguish the flamepropagation.

Referring to FIG. 11, the pore size is determined based on the criticaldiameter. The critical diameter is the minimum pipe diameter below whicha detonation of a specific fuel/oxidizer combination will not propagatebecause the detonation cell structure cannot exist. When a flame travelsto a flashback arrestor having a pore size smaller than the detonationcell size of the detonation wave, the flame will be quenched and stoppropagating because the detonation cell does not exist when thedetonation wave travels through the pores.

Therefore, the target pore size in accordance with the teachings of thepresent disclosure is based on critical tube diameter data, which iscalculated from cell width data for oxy-acetylene worst case initialpressure and stoichiometry conditions. Acetylene (C₂H₂) is used as thefuel gas in determining the desired pore size of the flashback arrestorsbecause acetylene is the most volatile and has the highest burningvelocity. As long as the determined pore size of the flashback arrestorscan stop generation of the oxy-acetylene detonation cell, the determinedpore size can also stop generation of the detonation cell by a mixtureof oxygen and other fuel gases.

FIG. 11 shows the critical tube diameter (cell width/Pi) for a range ofavailable initial pressure data when the oxy-fuel mixture has anequivalence ratio (ER) of 2.5 (˜47.5% fuel by volume). The equivalenceratio is the ratio of the fuel-to-oxidizer ratio to the stoichiometricfuel-to-oxidizer ratio (˜28.5% fuel by volume). The stoichiometric ratiois the xoy-fuel ratio necessary for complete combustion. The acetylenepressure of 22.5 psig (37.2 psia) is considered worst case based onoperating pressures in Europe. Therefore, from the curve fit equation,the cell width for oxy-acetylene detonations at this initial pressurewould be approximately 49 μm (0.0019 in). The critical tube diameterassociated with this cell size is approximately 16 μm (0.0006 in).

Curve fits of these data allow specifying a target cell width orcritical tube diameter for a given pressure. The curve fit equation forcell width (A) for oxy-acetylene mixtures with an ER of 2.5 is:

λ=1309.2×(P)^(−0.907)

where: λ=cell width (microns)

-   -   P=initial mixture pressure (psia)

The geometry of sintered metal pores is not circular and thusapplication of the critical tube diameter for a given stoichiometry andinitial pressure would not necessarily directly apply. The criticaldimension would likely be between the values of cell width (typicallyapplicable to square or rectangular geometries) and cell width dividedby Pi (typically applicable to circular geometries). Based on thislogic, the critical dimensions (true pore size) for arresting anoxy-acetylene detonation (Equivalence Ratio=2.5) is estimated to bebetween 16 μm to 49 μm.

The maximum acetylene pressure that is recommended for use in NorthAmerica is 29.7 psia, whereas Europe and other parts of the world allowacetylene pressure to be used at 37.2 psia. With these parameters, theresearch and testing result in a determined detonation cell width sizeof 0.0019″. By dividing the detonation cell width by pi, the criticaldiameter of 0.0006047″ (or 15.4 μm) is achieved.

As shown in FIG. 12, the detonation cell size is increased as theinitial pressure is decreased. The oxy-acetylene mixture is at astoichiometric ratio (28.5 volume % fuel). The C₂H₂—O₂ detonationindicates that the detonation cell width ranges from ˜0.003 to ˜0.006inches at 15-30 psia at the stoichiometric ratio (28.5 v % fuel). Forexample, when the pressures are 14.9 psia, 30.4 psia, and 44.3 psia, thecell widths are 0.169 mm (0.0067 in), 0.081 mm (0.0032 in) and 0.059 mm(0.0024 in), respectively.

As shown in FIG. 13, the oxy-acetylene mixture has an equivalence ratioof 2.5 (i.e., 47.5% fuel by volume). When the pressure is 14.6 psia,30.0 psia, and 60 psia, the detonation cell width is 0.109 mm (0.0043in), 0.059 mm (0.0029 in), and 0.031 mm (0.0012 in), respectively. It isclear from FIGS. 11 and 12 that the cell width is decreased when aricher fuel-to-oxidizer mixture is used.

FIG. 14 shows the stoichiometry effect on the determination of thedetonation cell size. When the fuel-to-oxidizer is below thestoichiometric ratio, the detonation cell size increases abruptly. Whenthe fuel-to-oxidizer is higher than the stoichiometric ratio, thedetonation cell width is approximately the same when the equivalenceratio is between 1 and 2.5 and then gradually increases when theequivalence ratio is above 2.5.

FIG. 15 shows the detonation velocity increases when the oxy-fuelmixture has a higher percentage of fuel up to approximately 55% of thefuel. The detonation velocity then decreases as the ratio of fuel tooxygen is increased until the ratio of fuel to oxygen is 70%.

FIG. 16 is graph of the relationship between the detonation velocity andthe tube diameter for different oxy-acetylene mixtures. A richeroxy-acetylene mixture has smaller tube diameter and thus smallerdetonation width.

To provide a degree of safety and allow for variances in the manufactureof sintered filters, a pore size in the range of 10-14 μm can be viablyused. The lower limit of this range is greater than the pore size of 7μm in a typical flashback arrestor. The increased pore size of theflashback arrestors of the present disclosure increases flow capacity ofthe sintered porous body. Due to the increased flow capacity, thephysical size of the porous body can be reduced. The reduced size of theporous body allows the distal threaded portion of the fittings, which isused to secure the flashback arrester to the torch body or an add-onsafety device, to have a size adapted for a bore of a ¼-18 NPT pipethread, which is a standard thread in most oxy-fuel torches as a meansto join a hose connection to the torch body. As such, the flashbackarrestor of the present disclosure can be relatively easily mounted tothe bores of most oxy-fuel torches.

Moreover, by installing the filter directly into the bore of the fittingproximate to the proximal threaded portion, the flashback arrestors ofthe present disclosure can achieve the advantage of material reduction.In addition, the flashback arrestors of the present disclosure aresmaller than the typical flashback arrestors and have a simpler designwith fewer components. Therefore, the flashback arrestors can reducemanufacturing costs.

The description of the disclosure is merely exemplary in nature and,thus, variations that do not depart from the substance of the disclosureare intended to be within the scope of the disclosure. Such variationsare not to be regarded as a departure from the spirit and scope of thedisclosure.

What is claimed is:
 1. A flashback arrestor for use in gas cutting or welding equipment comprising: a porous body defining a proximal end portion and a distal end portion and having a plurality of pores, each of the pores defining a pore size, wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the sintered body.
 2. The flashback arrestor according to claim 1, wherein the pore size is between approximately 10 and approximately 16 microns.
 3. The flashback arrestor according to claim 1 further comprising a fitting disposed at the proximal end portion, the fitting being adapted to secure the flashback arrestor to the gas cutting or welding equipment.
 4. The flashback arrestor according to claim 3, wherein the fitting is sized to fit within a bore of a standard pipe thread.
 5. The flashback arrestor according to claim 4, wherein the standard pipe thread is a ¼-18 National Pipe Thread (NPT).
 6. The flashback arrestor according to claim 3 further comprising a filter disposed within the fitting.
 7. The flashback arrestor according to claim 1, further comprising an end cap secured to a distal end portion of the porous body.
 8. The flashback arrestor according to claim 1, wherein the porous body is formed with a sintering process.
 9. The flashback arrestor according to claim 1, wherein the pores define passageways through the porous body having irregular shapes.
 10. The flashback arrestor according to 1, wherein the sintered body defines a cylindrical geometry.
 11. A flashback arrestor for use in gas cutting or welding equipment comprising: a body defining a proximal end portion and a distal end portion and having a plurality of pores, each of the pores defining a pore size, wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
 12. The flashback arrestor according to claim 11, wherein the body is sintered.
 13. The flashback arrestor according to claim 11 further comprising a fitting disposed at the proximal end portion, the fitting being adapted to secure the flashback arrestor to the gas cutting or welding equipment.
 14. The flashback arrestor according to claim 13, wherein the fitting is sized to fit within a bore of a standard pipe thread.
 15. The flashback arrestor according to claim 13 further comprising a filter disposed within the fitting.
 16. The flashback arrestor according to claim 11, wherein the pore size is between approximately 10 and approximately 16 microns.
 17. The flashback arrestor according to claim 11, wherein the pore size is a function of an initial pressure of a gas mixture and an equivalence ratio of the gas mixture.
 18. The flashback arrestor according to claim 17, wherein the pore size λ is defined by the equation: λ=1309.2×(P)^(−0.907) wherein P is the initial pressure of a mixture of oxygen and acetylene having an equivalence ratio of about 2.5.
 19. A device for arresting a flame comprising: a body having a plurality of pores, each of the pores defining a pore size, wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
 20. The device according to claim 19, wherein the body is sintered.
 21. A flashback arrestor for use in gas cutting or welding equipment comprising: a sintered body defining a proximal end portion and a distal end portion and having a plurality of pores, each of the pores defining a pore size; a fitting disposed at the proximal end portion, the fitting being sized to fit within a bore of a standard pipe thread, wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the sintered body.
 22. The flashback arrestor according to claim 21 further comprising a filter disposed within the fitting.
 23. The flashback arrestor according to claim 21, wherein the pore size is between approximately 10 and approximately 16 microns.
 24. An oxy-fuel cutting/welding torch comprising: a torch body defining a proximal end portion and a distal end portion; an oxygen passageway having an inlet at the proximal end portion; a fuel passageway having an inlet at the proximal end portion; a first flashback arrestor disposed within the oxygen passageway at the proximal end portion; and a second flashback arrestor disposed within the fuel passageway at the proximal end portion, wherein each of the first and second flashback arrestors define a body having a proximal end portion and a distal end portion and comprise a plurality of pores, each of the pores defining a pore size, wherein the pore size is a function of a detonation cell size such that the pore size is increased to reduce a size of the body.
 25. The oxy-fuel cutting/welding torch according to claim 24, wherein the bodies of the flashback arrestors are sintered.
 26. The oxy-fuel cutting/welding torch according to claim 24 further comprising: a first fitting disposed at the proximal end portion of the first flashback arrestor; and a second fitting disposed at the proximal end portion of the second flashback arrestor, the fittings being adapted to secure the flashback arrestors within the passageways of the oxy-fuel cutting/welding torch.
 27. The oxy-fuel cutting/welding torch according to claim 26, wherein the fittings are sized to fit within a bore of a standard pipe thread
 28. The oxy-fuel cutting/welding torch according to claim 28 further comprising: a first filter disposed within the first fitting; and a second filter disposed within the second fitting.
 29. The flashback arrestor according to claim 24, wherein the pore size is between approximately 10 and approximately 16 microns.
 30. A device for arresting a flame comprising: a body having a plurality of pores, each of the pores defining a target pore size, wherein the pore size is a function of an initial pressure of a gas mixture and an equivalence ratio of the gas mixture such that the pore size is increased to reduce a size of the body.
 31. The device according to claim 30, wherein the target pore size λ is defined by the equation: λ=1309.2×(P)^(−0.907) wherein P is the initial pressure of a mixture of oxygen and acetylene having an equivalence ratio of about 2.5. 